Two field experiments were carried out in sandy soil during the summer seasons of 2003 and 2004at Siwa Oasis, Egypt (26.0°N, 29.0°E and 0-22 m under mean sea level). The experiments were irrigated by using drip irrigation system with  salinity water of 6000 p.p.m), Cowpea, Vigna unguiculata cv. Cream 7 cultivar was cultivated to study the effect of inoculation by three methods ( inoculation of   seeds pre-sowing, as soil application  by injection of  inoculation after germination and  with both methods on the growth and yield of cowpea. There were four inoculation treatments represented in new strain of Rhizobia (Rh), Bacillus megatherium phosphate dissolving bacteria (P. D. B.) and mixed inoculation (Rh + P. D. B.)  in addition to control. The data were recorded for vegetative growth characteristics (plant height (cm), No. of branches, fresh and dry weight/ plant (g) and leaf area (cm²)). Also, dry pods yield and its components (No. of pods/plant, average pod weight (g), seeds number / pod, seeds yield (g)/plant and  (kg)/fed.). Chemical constituents of dry seeds (N %, P %, K %, protein % and carbohydrate %) were determined. Obtained results showed that inoculation  of seeds pre-sowing and inoculation of  soil after germination together surpassed than other methods in growth characters, yield and its components as well as chemical composition. The same trend was observed for the inoculation with  Rh + P. D. B. treatment when compared to other inoculation treatments. The highest values of growth characters, yield and its components and chemical composition of cowpea (Cream 7 cultivar) were obtained with interaction treatment between  inoculation of seeds pre-sowing and inoculation of soil after germination and Rh + P. D. B inoculation . The results were true in the two growth seasons.